The present invention relates to the field of breast lesion localization, and more particularly to an improved dual mode method and apparatus for localizing a breast carcinoma lesion using both nuclear medicine (scintimammography) and X-ray techniques to obtain localization results more accurate than prior art methods using only a single technique.
X-ray mammography is the primary clinical screening tool for breast cancer. Over 15 million mammograms were performed in 1995 and over 25 million are expected to be performed by 2000. However mammography suffers from a high false positive rate. Currently, biopsies are performed following a positive mammogram to determine whether a suspicious lesion is cancerous or benign. Of the approximately 800,00 biopsies performed in 1995, roughly 600,000 were conducted on benign lesions. In addition to the expense involved, biopsy is a stressful procedure for the patient and the scarring left by the biopsy makes subsequent mammograms more difficult to interpret. Additionally, about 15-25% of all women have breast tissue that results in indeterminate mammograms. Dense tissue and scarring from prior surgery have x-ray densities similar to breast lesions, resulting in low contrast mammograms that are difficult to interpret.
Scintimammography has been shown to be able to complement mammography by imaging the metabolic activity of cancerous lesions while ignoring benign lesions is and healthy tissue. In studies conducted over the past five years involving 600 women, in connection with the approval process of the DuPont Merck Pharmaceutical Company imaging agent Miraluma(trademark), it was concluded that scintimammography is useful in differentiating cancerous and benign lesions. However, the studies also concluded that current large field-of-view gamma cameras cannot reliably image breast lesions smaller than 1.2-1.5 cm. In addition, the large size of these cameras limits-their use to the lateral (side) views and does not allow for imaging the breast from other desirable viewing angles, and lesions in the chest wall are very difficult to detect.
Stereotactic breast biopsy is an X-ray guided method for localizing and sampling breast lesions discovered on mammography and considered to be suspicious for malignancy. Guided core biopsy is a relatively new procedure that has been shown to have many advantages over surgical biopsy in the form of reduced patient anticipation and discomfort. In this procedure, that is typically performed in the physician""s office, the patient lies on a mammography table and the affected breast is pendantly positioned through a hole in the table in a specially designed pair of compression paddles. The physician then obtains a computerized picture of the breast and determines with varying degrees of precision the position of the suspicious breast lesion. The standard X-ray tube can be movably located perpendicular to the X-ray detector as well as +15xc2x0 and xe2x88x9215xc2x0 to the perpendicular. Localization of a specific lesion within a breast under examination is based on measurements of the position of the lesion on at least two images (a stereo pair) of the breast taken at different angles. The radiologist selects the center of the lesion, mass, or calcification and a computer generates the Cartesian coordinates of the targeted area. Once the stereo pair is generated and the computer calculates the location of the targeted area, one of several devices is employed to obtain a tissue sample for biopsy.
Further, it is well known that nuclear medicine-based gamma camera systems that rely on nuclear medicine based techniques involving the injection of a suitable radio-pharmaceutical that is preferentially absorbed by cancerous tissue and detected by a gamma radiation sensitive camera device are highly more accurate in distinguishing between cancerous and benign lesions.
U.S. Pat. No. 5,595,177 to Mena et al issued Jan. 21, 1997 and U.S. Pat. No. 5,803,913 to Khalkhali et al issued Sep. 8, 1998 both disclose nuclear-medicine based apparatus, systems and methods for streotaxic localization of potential breast carcinoma lesion sites.
U.S. Pat. No. 5,289,520 to Pelligrino et al issued Feb. 22, 1994 describes a stereotactic mammography imaging table and system with X-ray projection to a CCD camera that permits detailed optical examination and analysis of the X-ray image.
None of these references discloses the combined use of an X-ray imaging device and a nuclear medicine imaging device in a single system to obtain a more accurate localization of a potentially cancerous lesion. This lack of disclosure is due to the relatively large size of both the X-ray imaging and prior art nuclear imaging or gamma camera devices that have rendered the incorporation of both such devices in a single apparatus impossible until now.
U.S. patent application Ser. No. 09/425,409 filed Oct. 25, 1999 describes a dual mode method and apparatus for obtaining highly accurate stereotactic images of potentially cancerous lesions by making use of both X-ray and scintimammographic stereo images by acquiring both images from different angles through movement of the two imaging devices. Obtaining of the scintimammographic images is made possible through the use of an improved and significantly smaller gamma camera device that can be inserted and maneuvered within the sometimes-crowded environment of the examination area. Elimination of the need to move the gamma camera for purposes of obtaining the image pair required for stereotactic scintillation imaging would provide an even further improvement by reducing that amount of room required in the examination area for gamma camera maneuvering in connection with obtaining the second such image.
It is therefore an object of the present invention to provide an improved gamma camera that eliminates the need for repositioning the gamma camera for purposes of obtaining a stereo pair of images.
It is another object of the present invention to provide a method for obtaining a stereo pair of scintimammographic images that involves the simple rotation of slant-hole collimator thereby eliminating the need for space in the examination area to reposition the gamma camera for this purpose.
The invention described herein combines the structural digital X-ray image provided by conventional Lorad or Fischer-type stereotactic core biopsy instruments with the additional functional metabolic gamma imaging obtained with a dedicated compact gamma imaging mini-camera but without the need for relocating the gamma camera in order to obtain a stereo pair of scintimammographic images as described in aforementioned U.S. patent application Ser. No. 09/425,409. Before the procedure, the patient is injected with an appropriate radiopharmaceutical, such as Miraluma from E.I. DuPont or other specific breast-imaging agent. The radiopharmaceutical uptake distribution within the breast under compression in a conventional examination table expressed by the intensity of gamma emissions is obtained for comparison (co-registration) with the digital mammography (X-ray) image. This dual modality mode of operation greatly increases the functionality of existing stereotactic biopsy devices by yielding a much smaller number of false positives than would be produced using X-ray images alone. The ability to obtain both the X-ray-mammographic image and the nuclear-based medicine gamma image using a single device is made possible largely through the use of a novel, small and movable gamma imaging camera that permits its incorporation into the same table or system as that currently utilized to obtain X-ray based mammographic images for localization of lesions. Elimination of the need to maneuver or relocate the gamma camera to obtain the stereo image pair is made possible through the use of a slant-hole collimator in the gamma camera. The collimator is capable of being rotated or re-oriented to obtain two angularly different scintimammographic images without repositioning the gamma camera.